Static frequency changer



March 3, E

STAT IC FREQUENCY CHANGER Filed Oct. 26, 1939 2 Sheets-Sheet 1 2/ I M y y be 26 .z\ /8 v m F [G I I II m w [1 |L ll V II II 4 l5 l5 i 11 34 @n Y 33 E F/ai I Henry-Mart: Huge INVENTOR' BY Q mw 1M March 3, E I

STATIC FREQUENCY CHANGER Filed Oct. 26, 1959 2 Sheets-Sheet 2 Henry Marl/)2 ffuye INVENTOR.

BY QMMM 1M Patented Mar. 3,

s'rA'rrc mEQUENcycnANoEn Henry Martin Huge, Lorain, Ohio, assignmof 1 f one-half to E. M. Heaven and one-half to Closman P.8tock er i j Application October 26, 1939, Serial No. 301,469

, 19 Claims. This invention relates to static frequency changers and more particularly to static frequency changers which depend for their operation upon the saturation of magnetic core materials. Specifically my invention has for its purpose the generation of a .plurality of frequencies which may be used for signaling purposes in telephone or-other electrical systems.

It is an object of this invention to produce without any moving parts two or more signaling tones which are easily distinguishable from each other.

Another object of my invention is to provide a tone signaling'device capable of operating over wide variations of input voltage.

It is another object of my invention to generate even harmonics of the input frequency without the use of permanent magnets or direct current.

a harmonic generator for producing even har-' monics when self-excited by'alternating current. Another object of my invention is to produce harmonics in the output wave generated by a' frequency changer.

A further object of my invention is to pro- 1.

duce even harmonics in the output wave generated by a frequency changer.

Another object of nay-invention is to double a frequency and produce harmonics of the doubled frequency.

It is another object'of my invention to obtain in the output of a frequency mult plier the de sired frequency with substantially all of the frequencies lower than the desiredfrequency eliminated.

It is another object of my invention to generate simultaneously a frequency with a modulated wave and a frequ ncy with an unmodulated wave from a frequency changer which depends upon magnetic saturation for operation.

It is another object of my invent on to provide improved stabilizing means for a static type frequency changer. I

Another objectof my, invention is to produce in a frequency, changer, harmonics of the outcharacteristic also adds stability to the circuit quency changer by the use of an inductance with a saturable core in the output circuit.

Another objector my invention is to provide a frequency changer inwhich the generation of the new frequency is substantially unaffected by variations in load.

It is another object of myinvention toproduce in a frequency changer, a frequency with a modulated wave and a frequency with an unmodulated wave each of which is substantially free and independent of' the load variations on the other.

' It is another object of my invention to produce in a. frequency changer, two different output frequencies, one of which is a modulated wave and the other an unmodulated wave. 7

Other objects anda fuller understanding of my invention may be had by referring to the following description and claims, taken in conjunction with the accompanying drawings, in which like parts are designated bylike reference characters, and in which: r

Figure 1 shows a static type frequency changer which is equipped with an output circuit adapted to furnish a tone suitable for signaling purposes and capable of producing evenharmonics of the input frequency.

Figure 2 shows a simple output network adapted to be connected to the secondary of the frequency changer to aid in self-excitation and to increase the harmonic content of the output voltage.

Figure 3 comprises the joining of the subject matters of Figures 11 and 2.

Figure 4 shows a rectifier'in the output network. which introduces even harrnonics in the output voltage and because of its non-linear operation, and t Figure 5 shows the preferred embodiment of my invention when using a common magnetic core in the main part of the frequency changer My invention relates to a static type frequency changer and in the present application 1 will describe it as being designed to operate in conjunction with the automatic switching apparatus in dial type-telephone offices but 'myinvention may find utility in operation with other electrical systems; As is well known to those put frequencyland. to accentuate one. or more of these harmonics. j

It is a further object of my invention "to improve the output voltage regulationfrom a freskilled inthe art, the dial type telephone utilizes tones for signaling purposes. For instance, dial tone indicatesto a userthat the telephone is ready for use, and an. interrupted tone is often used to indicate a busy line condition. There I are many other uses for tone in the automatic telephone systems, but at the present time, all necessary functions can be performed by two different tones.

At present, these tones are generated by rotating equipment for the large oflices or by vibrating contact equipment for the small dial ofllces. In either case these units are adapted to oper ate from battery and furnish high tone and low tone. Such tone generators are subject to maintenance difficulties. Particularly, with the vibrating contact type of tone generating equipment-there is the problem of eliminating radio interference, preventing noise from entering the talking battery, and maintaining contact adjustment.

It is customary to use frequencies of the order of 500 cycles per second for the high tone and frequencies between 120 and 180 cycles per second for the low tone. However, in order to make the low tone transmit well over the telephone circuits, it is necessary to provide ample components of frequencies higher than 120 and 180 cycles in the tone. From a study of the art of static frequency changers one might be inclined to conclude that suitable frequencies might be obtained from prior types of static frequency changers for use as high and low tones in telephone signaling systems. However, from a practical standpoint there have been numerous difiiculties to retard the adoption of any such prior schemes.

For example, in order to obtain suitable tones from the old type of static frequency changers elaborate flltercircuits were required in order to obtain a good clear note which would transmit well. It was also difficult to obtain tones from the static type frequency changer which sounded like the tones in use in the telephone industry. In addition the increased cost of the old static equipment over the cost of the vibrating type equipment further retarded its adoption. By means of my invention I am able to make a simple static type tone generator which almost exactly duplicates the tones derived from former tone generating systems and is inexpensive enough because of the elimination of complicated filters and other equipment, to compare favorably with the most inexpensive apparatus available today. Furthermore, in my device there are no adjustments, no contacts to maintain, and the device positively cannot produce radio interference or introduce noise into the talking battery.

With reference to Figure l, I show transformers H and I2 having primary windings l3 and H connected in series with each other, with capacitor 22 and with a source of alternating current I 0, forming a ferro-resonant circuit. Secondary windings l5 and ii are connected so that practically no voltage of the frequency of source appears across the terminals 25 and 26 when the circuit to condenser IT is open. A circuit arrangement as shown in Figure 1 has a tendency to generate even harmonics of the frequency of source [0 and this tendency can be greatly enhanced by tuning the circuit to an even harmonic of source it) by a suitable capacitor IT and linear inductance 35.

With capacitor l1 and linear inductance 35 connected to secondary windings l and IS a closed self-exciting circuit is established and a current of a harmonic frequency flows therein and self-excites the saturable magnetic paths of the transformers II and I2 to produce an increased transfer of energy from the primary windings to the secondary windings. When the circuit is properly adjusted this self-exciting action is cumulative and the current builds up until it reaches an operating value. Such a circuit may be characterized as a closed self-exciting circuit. The terms closed self-exciting circuit," self-exciting circuit" or self-exciting alternating current circuit means," as used in this application refer to a frequency changing circuit in which the conversion of energy to the new frequency from the supplied frequency is accomplished through the effects on the saturable magnetic paths of the flow of current of the new frequency, In my invention the flow of alternating current in the self-exciting circuit produces instantaneous differences between the degrees of magnetization of the two saturable magnetic paths, and it is this difference of magnetization which makes possible the transfer of energy from the source ID to the self-exciting circuit. In the self-excited circuit, the self-excitation of the saturable magnetic paths results from a leading current flowing through a capacitor. The cooperation of self-excited circuit and the ferro-resonant circuit is a distinguishing feature of my invention. Under an operating condition many harmonics of source ll other than the frequency tuned by capacitor I1 and linear inductance 35, are present in the circuit. It is therefore possible to obtain a low tone directly from the secondary circuit. Taps 23 and 24 may be used for this purpose, or separate windings could be used. However, when load is taken directly from the secondary windings it has a detuning effect and under some load conditions the circuit becomes inoperative.

In order to avoid this detuning effect, I prefer to obtain the current for producing the low tone from a low tone output circuit comprising a transformer l8, and a capacitor 2i connected in series with the primary winding I! of the transformer H3. The load is supplied from the secondary winding 20 of transformer l8.

From test observations, I find that a distinctive low tone is obtained by energizing the low tone output circuit with voltage from either of the primary windings l3 and ll of the transformers II and I2 or with voltage mostly from either one of the two primary windings. In Figure 1, the low tone output circuit is connected across the primary winding ll of the transformer l2, but may be connected across the primary winding i3 of the transformer H. The low tone output circuit may also be energized with voltage from either of the secondary windings l5 and I6 or with voltage mostly from either one of the two secondary windings.

The low tone supplied by the low tone output circuit is made up of a number of frequencies. The capacitor 2| and the transformer l8 are so proportioned that the low tone output circuit is resonant to a frequency higher than the frequency of source in. In the case where the tone generator is used with telephone equipment this resonant frequency would be in the neighborhood of 600 cycles or higher.

A desirable feature of my low tone output circult is that a load on output winding 20 can never stop the flow of low frequency current flowing through windings l5 and I8 because at this low frequency the impedance oi capacitor 2| is made large compared with the impedance of winding i9. With this construction, load on winding 20 does not appreciably ailect the remainder of the frequency changer.

It should be pointed'out that either or both of transformers H and I2 may be auto-transformers, and in particular, when the ratio of transformation is one to one, one of the transformers may be a simple choke and the other a center tapped transformer.

The use of capacitor 22 makes it possible to operate transformers I and I! at saturation and to maintain a saturated condition over wide variations of the voltage of source |lI.- To obtain this result I adjust the primary circuit including capacitor 22 and windings l3 and H to jump into ferro-resonance. Capacitor 22 also'causes the circuit to generate a higher percentage of harmonies. is apparently a result of the increase of harmonies in the input current caused by the introduction of capacitor 22. I have found that the optimum value of capacitor |I depends upon the value of capacitor 22 for a given setup and in the samples tested the harmonics generated were increased by simultaneously increasing capacitors l1 and 22 as long as ferro-resonance was maintained in the input circuit.

It is possible to use a substantially linear inate without the use of linear inductance 35, but the harmonic content of the output voltage onwinding 20 is reduced by removing this inductance, and the circuit becomes less stable in its operation. The inductance 25 seems to cause a more pronounced modulation to take place in the low tone circuit consisting of capacitor 2| and winding IS on transformer I8. This is probably due to the fact that there are more harto which the high tone load circuit may be connected, includes a negative resistance character- This improvement in harmonic output monies in the voltage induced in winding ll on how I may obtain a low tone from my static frequency changer. I shall now explain how to obtain a high tone from the same frequency changer.

To obtain a supply of high tone from my -frequency changer I have developed a simple output network of the type shown in Figures 2 and 3.

The terminals 21 and 28 of Figure v2 may be connected to the terminals 25 and 26, or to taps indicated generally by the reference characters 23 and 24. When connected to the terminals 28 and 26 the Figure 3 is evolved. In the high tone output network, capacitors 29 and J0 and inductance 3| are adjusted so that the predominant frequency component of the. current flowing through Primary winding 38 of cutout transformer I2 is the desired frequency. Although I refer to Figure 2. as a simple output network, the

circuit cooperates with the main frequency.

changing circuit to produce a new and improved result.

According to my invention. I take advantage istic under certain operating conditions. This characteristic depends upon capacitor l1 and when the circuit of Figure 2 is connected to terminals 25 and 28 the negative resistance characteristic also depends upon the magnitude and phase angle of the current into the output net- .work.

In this combined circuit the impedances may be so adjusted that the current of the desired peres, although the current through capacitor 29 was maintained at approximately 250 miiliamperes.

According to my invention it is possible either to obtain an abundance of harmonics in the high tone output or to obtain an approximately sinusoidal output voltage. If the harmonics are desired I prefer to operate the core of transformer 22 at or near saturation which also tends to maintain thegoutpu't voltage within narrower limits. When the more nearly sinusoidal output voltage is desired transformer 32 should be made approximately .linear. Also, I prefer to have the impedance of the primary winding 33 low compared with the impedance of inductance 8|. It is to be understood that inductance 3| is approximately linear. Under this condition the current passing through these windings is nearly sinusoidal, and when the core of transformer 32 is saturated, the output voltage across secondary winding 34 contains considerable harmonics. It is possible to place primary winding 33 in series with capacitor 30 instead of in series with inductance 3|, but under this condition, even though the impedance of winding ll may be small compared with the impedance of capacitor 30, a distortion of current wave shape occurs which reduces the harmonic content of the voltage across secondary winding 34. If a Y more nearly sinusoidal output wave shape is deof the fact that the impedance looking into Y terminals 25 and 28 of transformers ii and I2 sired, it can be obtained by making high tone transformer 32 more nearly linear as was previously mentioned, and in thiscase primary winding 33 may be placed in series with either inductance II or capacitor Iii.

By making the impedance of primary winding impedance of tuning 23 low compared with the inductance 2|. I am able to prevent'variations in load from disturbing the tuning of the output network. I

In general the output network shown in Figures 2 and 3 acts as a high-pass filter in additionto its function of aiding in the generation of the desired -frequency. However, it will be recogn zed that output transformeru being in series not constitute the with inductance 3| dces normal type of high-pass filter circuit.

The inductance 35 makes it possible to tune capacitor I! much more. closely with windings I8 and I6 and also stabilizes the operation of the entire circuit. The stabilizing action of inductance 36 increases the operating range of the frequency changer. Under tests the frequency changer operated satisfactorily over a maximum range of 103 to 127 volts without stabilizing inductance 35. By the addition of stabilizing inductance 35 the frequency changer operated satisfactorily over input voltage ranges from 80 volts to 140 volts. Although the exact theory explaining the operation of stabilizing inductance 35 may be subject to debate, one theory for its effective action is that it tends to prevent the flow of the higher harmonics through capacitor i1 and to force these higher harmonies through capacitors 29 and 30, although I do not intend to be bound to this theory. In effect, inductance 35 seems to function to separate the frequencies flowing through capacitor 17 and the frequencies flowing through capacitors 29 and 30. Although I have shown inductance 35 in series with capacitor i1 only in Figures l and 3, it is to be understood that it may be added to Figure 4. As explained with reference to Figure l, inductance 35 also improves the low tone from output winding 20.

By supplying 60 cycles from source ID in Figure 3, it is possible to obtain 480 cycles from output winding 34. This frequency is suitable for use as high tone in the telephone systems. However, the amount of power available from winding 34 is comparatively small with respect to the power input and what is more important the tone generated does not sound like the tone obtained from vibrating tone generating equipment. It is believed that this difference in sound is due to the fact that the tone obtained from winding 34 does not contain enough even harmonics of the output frequency. Therefore to make the timbre of the high tone obtained from the static type tone generator comparable to the tone generated by the vibrating type equipment, I have modified Figure 3 and developed the circuit shown in Figure 4.

Figure 4 diflers from the previous figures by the addition of rectifier bridge 36 in series with tuning inductance 3| of the output network. The addition of rectifier 36 to the output net 'work including inductance 3| performs two functions, first it introduces even harmonics into the load circuit, and secondly, because of the non-linear characteristic of the rectifier, the stability of the entire circuit is-improved. I have found that if an adjustable resistor is substituted for rectifiers 36 that stable operation of the frequency changer circuit can be maintained if the value of the resistor is'increased as the input voltage from source III is decreased. As is well known, the impedance of the dry disc type of rectifier decreases as the voltage impressed upon the rectifier is increased. In the preferred operating range the current flow through inductance 3| and consequently through reotifiers 36 is reduced as the input voltage is decreased. Since a decrease in current flow through rectifiers 36 causes the resistance of rectifiers 35 to increase this change in resistance is in the proper direction to maintain stable circuit operation.

In order to deliver to the load a 480-cycle wave the output network is altered to cause a predominantly 240-cycle current to flow through tuning inductance 3i and rectifiers 36.

Rectifiers 36 are '50 arranged that they act as a full wave rectifier and therefore double the supplied frequency. Because of this characteristic ofa full wave rectifier 480 cycles is supplied to the load connected to the high tone output terminals 31 and 38. Because of. the non-linear characteristics of rectifiers 36, a high percentage of even harmonics of the 480-cycle wave is introduced into the high tone output voltage delivered to the load. The tone obtained from such a device is very similar to the tone delivered from present day vibrating equipment operated from a battery source. With this circuit, however, variations of load have an effect on the tuning of the frequency changer. In particular, it is essential that the load should not constitute an open circuit to the direct current from the rectifier bridge, because if it does the circuit will be detuned by the impedance of the rectifier bridge.

To overcome the disadvantages of the circuit of Figure 4, I prefer to make use of the arrangement shown in Figure 5, which is that of a complete tone generator utilizing a common core transformer type of construction and capable of supplying high and low tone. The primary winding 40 of the high tone output transformer 39 is permanently connected to the rectifier bridge 36, providing a path for the direct current. Furthermore, the D. C. resistance of this path is independent of load conditions on the secondary winding 4|. The arrangement shown in Figure 4 is particularly well adapted to furnish tone to a constant load, but when used with a variable load it is desirable to provide rectiflers capable of withstanding the voltage of an open circuit condition.

The rectifiers in the circuit of Figure 5 however, need to sustain only a small voltage, the value of which is determined by the resistance and impedance of winding 40. This arrangement makes possible to obtain a low tone voltage across winding 20 which is independent of the load condition of the high tone output circuit.

A further advantage of the arrangement of Figure 5 over that of Figure 4 arises from the fact that when the impedance of transformer 39 is properly proportioned, the presence of any frequencies lower than the desired frequency is minimized in the output.

I prefer to operate the core of transformer 39 at saturation to increase the harmonics in the output. The normal current wave shape from a rectifier bridge is characterized by a rapid rate of change of current when the current is low. By making transformer 39 saturated, I take advantage of this characteristic of the rectifiers. The impedance of winding 40 is small when the current magnitude is large, and its impedance is high when the current magnitude is small. Therefore, the rapid rate of change of current occurs at a time when the transformer is best suited to transmit a peaked voltage to the secondary. This peaked voltage is highly desirable in duplicating the tone produced by present vibrating equipment, and at the same time, the high harmonics present in the peaked voltage transmit well through telephone circuits.

Capacitor 42 across the primary winding 40 is proportioned so that a local anti-resonant circuit is formed, the anti-resonance frequency being of the order of some of the desired harmonics of the output frequency. The magnitude of these harmonics is therefore increased by the addition of capacitor 42.

The circuit shown in Figure 5 is the preferred form of my invention using a common core type of construction, and includes a new method of obtaining stable circuit operation by means of stabilizing auto-transformer 56 which will be described as the circuit is explained.

In Figure 5, the current from source l6 passes through capacitor 22 and windings 44 and 45 magnetizing core 43 to a sufficient degree to make its operating characteristic non-linear. The

windings are arranged so that when there is no current through winding "there is practically no magneto-motive force developed from windlugs 44 and 45 across the portion of core cluded by winding 41. 7

With capacitor I1 connected across at least a portion of winding 41 a current flows through winding 41 and capacitor l1. The flux induced by this current flow through winding" is superimposed on the flux already present in the core to cause changes in reluctance through the effect of the non-linear magnetization characteristic of core 43. These changes in reluctance produce additional coupling between winding 41 and windings 44 and 45, the coupling being a function of the current through winding 41. In operation the voltage induced in winding 41 depends upon that mutual impedance or coupling and the value of the capacitors I1, 29 and 30 and impedance of winding 55 of stabilizing transformer 54. connected to winding 41. If the proper phase angle exists between the current and voltage in winding 41, oscillations in the circuit including winding 41 will have a frequency which is a harmonicof the frequency of source i0. Furthermore, these oscillations are self starting and self sustaining.

I have found that stability of circuit operation can be maintained over wide variations of input voltage if the two oscillating circuits, one including condenser l1 being the self excitation circuit and the other including the rectiflers 36 being the high tone output network, are coupled as shown in Figure 5. Winding 55 on stabilizing transformer 54 is in the output oscillating circuit and winding 56 is in series with capacitor H in the self-excitation circuit. In eflect, winding through winding 41, I obtain a-low tone from output winding 20 which is a harmonic of 60 cycles modulated at 120 cycles. However, under certain conditions it is possible to make the 60-cycle component across winding modulate the higher frequency and obtain a harmonic of cycles from output winding 20 which is modulated at 60 cycles. It is therefore. to be understood that the modulating frequency may be controlled, and the quality of the low tone obtained from output winding 20 altered accordingly.

Capacitor l1 serves to maintain the proper phase angle in the self-exciting circuit to sustain oscillations of a frequency which is a harmonic of the frequency of source l0.

fiers and for this reason the network'is tuned to' pass 240-cycle current through rectifiers 45.

. Capacitor I1 is so selected as to pass predominantly second harmonic current and the presence 55 is used for tuning purposes and winding 55 v is used for stabilization. The exact manner in in which winding 55 stabilizes the circuit may be subject to debate, but I have found that reversing the phase of winding 55 with respect to winding 55 causes the circuit to become unstable. If winding 55 is used for tuning purposes and stabilizing winding 55 is omitted, the circuit is operative only over a very narrow range of input voltages with approximately the same high tone output as when the stabilizing winding 55 is used,

or if the maximum output is reduced the circuit of this second harmonic current improves the quality and quantity ofthe 4th harmonic current. In addition to the self-excitation-previously mentioned in this description and depending upon the phase relation between the 2nd and 4th harmonic currents, the action of-each current upon the saturation of the core 43 is such that it produces a voltage to reinforce the other current.

The actual values of harmonics selected above apply only to a given case and other harmonic voltages may be obtained by properly selecting the values of the capacitors and inductances used. When the frequency changer is 'usedto provide signal tone in telephone systems the harcapacitor 30 instead of in series with winding 55 may be made to operate over a somewhat wider I range of input voltage.

In a particular case, the stabilizing winding constituted approximately 8% of the total winding on transformer 54. By thus coupling the two oscillating circuits together, I have maintained stable circuit operation when the input voltage varied between '70 volts and 220 volts. When the input voltage was varied over a slightly narrower range, between volts and 210 volts, the current fiowing through winding 55 and therefore through rectiners 38 was maintained within limits of plus or minus-5%. With this high degree of stabilization the high tone output was practically constant over this range.

It is well to point out that either even or odd harmonics may be obtained from winding 41 on the core 43. By supplying 60 cycles from source III to a circuit as'shown in Figure 5, I have changed the predominant frequency flowing throughcondenser l1 and winding 41 from cycles to cycles merely by changing the tuning. With a frequency of 120 cycles flowing of stabilizing transformer 54 but in thisvcase the high tone output wave contains fewer high harmonic frequencies than when the circuit of Figures 4 and 5 are. followed, because the capacitors I1, 28 and 30 effectively short circuit the higher frequencies. However, when the impedance of winding 55 is in series with the output this high frequency appears inthe output wave.

As previously mentioned capacitor 22 is so selected that the input circuit including windings 44 and 45 operates in series-ferro-resonance from source l0. Changes in input voltage therefore have little effect on the voltage across windings 44 and 45. The tone generator being stabilized in operation by transformer 54, is capable of delivering an almost constant high tone outputfor a given load as the input voltage varies over a wide range. With the circuit shown in Figure 5 properly tuned, capacitor 22 aids in assuring that 'the oscillations through winding 41 are self-starting as well as self-sustaining.

In Figure 5, switch 58 is used to connect the circuit with source I, and fuse 59 is proportioned itor 22 when switch 58 is opened or fuse 59 operates.

It should be pointed out that in operation, a voltage may develop between the output network and ground due to an electrostatic field. While I have not shown the method of reducing this voltage I prefer to connect one point of the output network to ground through a high resistance. A 250,000 ohm resistor connected between a terminal on rectifier 35, as shown in Figure 5, and the metal cabinet has been found to reduce this potential to a satisfactory value.

Although I have described my invention with a certain degree of particularity, it is understood that the present disclosure has been made only by way of example, and that numerous changes in the details of construction on the combinations and arrangement of parts may be resorted to without departing from the spirit and scope of the invention as hereinafter claimed.

I claim as my invention:

1. A magnetic frequency changer adapted to. be energized by a suitable source of alternating current comprising, in combination, magnetic core means having two saturable magnetic paths substantially equal in magnetic characteristics, first winding means for magnetizing said two saturable magnetic paths to substantially the same flux density, second winding means embracing the two saturable paths, said first and second winding means being connected to induce substantially zero voltage of the frequency of the source of alternating currents in the second winding means, a plurality of tuned circuits connected to said second winding means, said plurality of tuned circuits receiving energy from harmonics of the current flowing in said first winding means, and output means connected to and receiving energy from at least one of said plurality of tuned circuits.

2. A magnetic frequency changer adapted to be energized by a suitable source of alternating current comprising, in combination, magnetic core means having two saturable magnetic paths substantially equal in magnetic characteristics, first winding means for magnetizing said two saturable magnetic paths to substantially the same flux density, second winding means embracing the two saturable paths, said first and second winding means being connected to induce substantially zero voltage of the frequency of the source of alternating currents in the second winding means, a plurality of tuned circuits connected to said second winding means, said plurality of tuned circuits receiving energy from harmonics of the current flowing in said first winding means, output means connected to and receiving energy from at least one of said plurality of tuned circuits, and second output means connected to and receiving energy from the first winding means.

3. A magnetic frequency changer adapted to be energized by a suitable source of alternating current and generating a new frequency comprising, in combination, magnetic core means having two saturable magnetic paths substantially equal in magnetic characteristics, first winding means for magnetizing said two saturable magnetic paths to substantially the same flux density, second winding means embracing the two saturable paths, said first and second winding means being connected to induce substantially zero voltage of the frequency of the source of alternating currents in the second winding means, and a self-exciting circuit including a capacitor connected to the secondary winding means to receive energy therefrom and establishing a leading current of a harmonic of the source to flow through the second winding means to self excite and bias the magnetic core means for generating the new frequency.

4. A magnetic frequency changer adapted to be energized by a suitable source of alternating current and generating a new frequency comprising, in combination, magnetic core means having two saturable magnetic paths substantially equal in magnetic characteristics, first wind ing means for magnetizing said two saturable magnetic paths to substantially the same flux density, second winding means embracing the two saturable paths, said first and second winding means being connected to induce substantially zero voltage of the frequency of the source of alternating currents in the second winding means, a self-exciting circuit including a capacitor connected to the secondary winding means to receive energy therefrom and establishing a leading current of a harmonic of the source to fiow through the secondary winding means to self excite and bias the magnetic core means for generating the new frequency, and output winding means and a capacitor forming a tuned circuit connected in circuit relation with a portion of the first winding means to supply a complex output wave having components including the frequency of the source of alternating current and the new frequency.

5. A magnetic frequency changer adapted to be energized by a suitable source of alternating current and generating a new frequency comprising, in combination, magnetic core means having two saturable magnetic paths substantially equal in magnetic characteristics, first winding means for magnetizing said two saturable magnetic paths to substantially the same fiux density, second winding means embracing the two saturable paths, said first and second winding means being connected to induce substantially zero voltage of the frequency of the source of alternating currents in the second winding means, a self-exciting circuit including a capacitor connected to the secondary winding means to receive energy therefrom and establishing a leading current of a harmonic of the source to flow through the second winding means to self excite and bias the magnetic core means for generating the new frequency, output winding means and a capacitor forming a tuned circuit connected in circuit relation with a portion of the first winding means to supply a complex output wave having components including the frequency of the source of alternating current and the new frequency, and an impedance element in series with the capacitor and the second winding means to form a substantially tuned self-exciting circuit.

6. A magnetic frequency changer adapted to be energized by a suitable source of alternating current and generating a new frequency comprising, in combination,'magnetic core means having two saturable magnetic paths substantially equal in magnetic. characteristics, first winding means for magnetizing said two saturabl magnetic paths to substantially the same flux density, second winding means embracing the two saturable paths, one of said winding means having at least two opposed operating windings, a first circuit including a first capacitor and a first inductance element connected in series with each other and in closed circuit relation with the second winding means, a second circuit including a second capacitor, a second inductance element and an output impedance element connected in series with each other and in closed circuit relation with the second winding means, and a third capacitor shunting the second-inductance element and the output impedance element;

7. A magnetic frequency changer adapted to be energized by a suitabl source of alternating current and generating a new frequency com prising, in combination, magnetic core means having two saturable magnetic paths substantially equal in magnetic characteristics, first winding means for magnetizing said two saturable magnetic paths to substantially the same flux density,'second winding means embracing the two saturable paths, one of said winding means having at least two opposed operating windings, a first circuit including a first capacitor connected in closed circuit relation with the second winding means, a second circuit including a second capacitor, a second inductance element and an output impedance element con-' nected in series with each other and in closed circuit relation with the second winding means, and a third capacitor shunting the second inductance element and the output impedance element. f 8. A magnetic frequency changer adapted to be energized by a suitable source of alternating current and generating a new frequency comprising, in combination, magnetic core means having two saturable magnetic paths substantially equal in magnetic characteristics, first winding means for magnetizing said two-saturable magnetic paths to substantiallyth'e same flux density, second winding means embracing the two saturable paths, one of said winding means having at least two opposed operating windings, a first circuit including a first capacitor connected in closed circuit relation with the second winding means, a second circuit including a second capacitor, a second inductance element and an output winding means connected in series with each other and in closed circuit relation with the second winding means, a third capacitor shunting the second inductance element and the output winding means, and a fourth capacitor in series with the first winding means to establish a series ferro-resonant ciri cuit.

9. A magnetic frequency changer adapted to be energized by a suitable source of alternating current and generating a new frequencycomprising, in combination, magnetic core means having two saturable magnetic paths substantially equal in magnetic characteristics, first winding means for magnetizing said two saturable magnetic paths to substantially the same flux density, second winding means embracing the two saturable paths, one of said winding means havingv at least two opposed operating windings, a first circuit including a first capacitor connected in closed circuit relation with the second winding means. a second circuit including a second capacitor, a second inductance element and'an output rectifier means connected in series with each other and in closed circuit relation with the second winding means, a third capacitor shunting the second inductance element and the output rectifier means, and a fourth capacitor in series with the first winding means to establish aseriegferro-resonant circuit.

10. A magnetic frequency changer adapted to be energized by a suitable source of alternating current and generating anew frequency comprising, in combination, magnetic core means having two saturable magnetic paths substantially equal in magnetic characteristics, first winding means for magnetizing said two saturable magnetic paths to substantially the same flux density, second winding means embracing the two saturable paths, one of said winding means having at least two opposed operating windings, a stabiliz'ng transformer having a first and a second winding portion, a first circuit including a first capacitor and the first winding portion of the stabilizing transformer connected in series and in closed circuit relation with the second winding means, a second circuit including a second capacitor, output rectifier means and the second winding portion of the stabilizing transformer connected in series and in closed circuit relation with the second winding means, a third capacitor shunting the output rectifier means and the second winding portion of the stabilizing transformer, and a fourth capacitor in series with the first winding means to establish a series ferro-resonant circuit.

11. A magnetic frequency changer adapted to be energized by asuitable source of alternating current and generating a new frequency comprising, in combination, magnetic core 'means having two saturable magnetic ,paths substantially equal in magnetic characteristics, first winding means for magnetizing said two saturable magnetic paths to'substantially the same flux density, second winding means embracing the two saturable paths, one of said winding means having at least two opposed operating windings, a first circuit including a first capacitor connected in closed circuit relation with the second winding means, a second circuit including a second capacitor, a second inductance element and an output impedance'element connected in series with each other and in closed circuit relation with the second winding means, a third capacitor shunting the second inductance element and the output impedance element, and output winding means and a capacitor forming'a tuned circuit connected in circuit relation with a portion of the first winding means to supply a complex output wave having components including the frequency of the source of alternating current and the new frequency.

12. A magnetic frequency changer adapted to be energized by a suitable source of alternating current and generating a new frequency comprising, in combination, magnetic core means having two saturable magnetic paths substantially equal in magnetic characteristics, first winding means for magnetizing said two saturable magnetic paths to substantially the same fiuxv density, second winding means embracing the two saturable paths, one of said winding means having at least two opposed operating windings,

a self-exciting first circuit including a capacitor.

the new frequency, a second circuit including a second capacitor, a second inductance element and an output impedance element connected in series with each other and in closed circuit relation with the second winding means, and a third capacitor shunting the second inductance ele-- ment and the output impedance element. i3. A-magnetic frequency changer adapted to be energized by a suitable source of alternating current and generating a new frequency comprising, in combination, a magnetizable coreprovided with two magnetic paths having a bridging member-in common, first winding means, second winding means, one of said winding means on each or said paths, a first circuit adapted to be connected to the said source and including a condenser and said first and second winding means in series to create alternating fluxes in said two paths which are in opposition in said bridging member, third winding means inductively related with said bridging member, and a selfexciting circuit including a second capacitor connected to the third winding means to receive energy therefrom and establishing a leading current of a harmonic of the source to fiow through the third winding means to self-excite and bias the magnetizable core for generating the new frequency.

14. A magnetic frequency changer adapted to be energized by a suitable source of alternating current and generating a new frequency comprising, inv combination, a magnetizable core provided with two magnetic paths having a bridging member in common, first winding means, second winding means, one of said winding means on each of said plaths, a first circuit adapted to be connected to the said source and including a condenser and said first and second winding means in series to create alternating fluxes in said two paths which are in opposition in said bridging member, third winding means inductively related with said bridging member, a first circuit including a first capacitor connected in closed circuit relation with the third windin means, a second circuit including a second capacitor, a second inductance element and an output impedance element connected in series with each other and in closed circuit relation with the third winding means, and a third capacitor shunting the second inductance element and the output impedance element.

15. A magnetic frequency changer adapted to be energized by a suitable source of alternating current and generating a new frequency comprising, in combination, a magnetizable core provided with two magnetic paths having a bridging member in common, first winding means, second winding means, one of said winding means on each of said paths, a first circuit adapted to be connected to the said source and including a condenser and said first and second winding means in series to create alternating fluxes in said two paths which are in opposition in said bridging member, third winding means inductively related with said bridging member, a first circuit including a first capacitor connected in closed circuit relation with the third winding means, a second circuit including a second capacitor, a second inductance element and an output impedance connected in series with each other and in closed circuit relation with the third winding means, a third capacitor shunting the second inductance element and the output winding, a fourth capacitor in serieswith the first and second winding means to establish a series ferro-resonant circuit,

. and an output winding means connected to the output impedance means and receiving energy therefrom.

16. A magnetic frequency changer adapted to be energized by a suitable source of alternating current and generating a new frequency comprising, in combination, a magnetizable core provided with two magnetic paths having a bridging member in common, first winding means, second and in closed circuit relation with the third winding means, a third capacitor shunting the second inductance element and the output rectifier means, and a fourth capacitor in series with the first and second winding means to establish a series ferro-resonant circuit,

17. A magnetic frequency changer adapted to be energized by a suitable source of alternating current and generating a new frequency comprising, in combination, a magnetizable core provided with two magnetic paths having a bridging member in common, first winding means, second winding means, one of said winding means on each of said paths, a first circuit adapted to be connected to the said source and including a condenser and said first and second winding winding means, one of said winding means on 76 means in series to create alternating fluxes in said two paths which are in opposition in said bridgingmember, third winding means inductively related with said bridging member, a first circuit including a first capacitor connected in closed circuit relation with the third winding means, a second circuit including a second capacitor, a second inductance element and an output impedance element connected in series with each other and in closed circuit relation with the third winding means, a third capacitor shunting the second inductance element and the output impedance element, and output winding means and a capacitor forming a tuned circuit connected in circuit relation with a portion of the first winding means to supply a complex output wave having components including the frequency of the source of alternating current and the new frequency.

18. A magnetic frequency changer adapted to be energized by a suitable source of alternating current and generating a new frequency comprising, in combination, a magnetizable core provided with two magnetic paths having a bridging member in common, first winding means, second winding means, one of said winding means on each of said paths, a first circuit adapted to be connected to the said source and including a condenser and said first and second winding means in series to create alternating fluxes in said two paths which are in opposition in said bridging member,. third winding means induc-' tively related with said bridging member, a selfexciting first circuit including a capacitor connected to the third winding means to receive energy therefrom and establishing a leading current of a harmonic of the source to flow through the third winding means to self-excite and bias the magnetizable core means for generating the new frequency, a second circuit including a second capacitor, a second inductance element and an output impedance element connected in series with each other and in closed circuit relation with the third winding means, and a third capacitor shunting the second inductance element and the output impedance element.

19. A frequency changer adapted to be energized by a suitable source of alternating current, comprising, in combination, a magnetizable core having two saturable magnetic paths with a bridging member in common, first winding means on each of said magnetic paths, said winding means being connected in series to induce opposing fluxes in said bridging member and being a part of a ferro-resonant circuit including said source, second winding means inductively related to the said bridging member, a plurality of self exciting circuits electrically connected to the second winding means, one of 10 from said rectifier.

HENRY MARTIN HUGE. 

